The noise figure (NF) and insertion gain of a radio receiver integrated circuit (IC) are often measured by applying two different levels of input noise and measuring the output power change, see, e.g., “Fundamentals of RF and Microwave Noise Figure Measurements,” Agilent Technologies Application Note 57-1, Oct. 12, 2006, “Noise Figure Measurement Accuracy—The Y-Factor Method,” Agilent Technologies Application Note 57-2, Mar. 19, 2004, and “10 Hints for Making Successful Noise Figure Measurements,” Agilent Technologies Application Note 57-3, Nov. 21, 2000, the disclosures of which are incorporated by reference herein.
The two different levels of noise are provided by a noise source, which often consists of a low-capacitance diode reverse biased into avalanche breakdown. However, at millimeter (mm) wave frequencies (approximately greater than 30 Gigahertz or GHz), the noise sources are expensive and difficult to manufacture. Furthermore, they are usually supplied with waveguide connectors which are difficult to connect to the radio frequency integrated circuit (RFIC) which is being tested. The wafer probes which are used to make electrical contact to the RFIC under test are themselves expensive and fragile, and they require precise mechanical manipulation to provide reproducible results.
An RFIC which has multiple RF inputs presents a particular problem, because any switch which might be used to switch one noise source to multiple RFIC inputs has insertion loss which interferes with the measurement accuracy, and the need to switch the noise source to multiple RFIC inputs also slows down the measurement, which is highly undesirable in a manufacturing environment. For instance, a receiver for a 4×4 phased-antenna array would have 16 inputs, and it would be prohibitive from a cost standpoint to provide 16 noise sources, while it would be unacceptable from a test time and test accuracy standpoint to switch one noise source to 16 RFIC inputs. Therefore, the techniques used to perform manufacturing tests on RFICs at microwave frequencies may be unacceptable at mm-wave frequencies.
Many electronic systems and ICs incorporate self-test features, see, e.g., Roeder et al., U.S. Pat. No. 6,834,991; Shrinkle, U.S. Pat. No. 5,585,974; Darabi et al., U.S. Pat. No. 7,233,772; Wu et al., U.S. Pat. No. 7,139,540; Moloudi et al., U.S. Pat. No. 6,917,789; Ziperovich, U.S. Pat. No. 5,737,342; Rofougaran et al., U.S. Pat. No. 7,082,293; G. Evans et al., “On-Chip Built-In Self-Test of Video-Rate ADCs Using a 1.5 V CMOS Gaussian Noise Generator,” 2005 IEEE Conf. on Electron Dev. and Solid-State Circuits (EDSSC), pp. 669-672; Tagawa et al., U.S. Pat. No. 4,772,945; and Hayashi et al., U.S. Pat. No. 6,779,144, the disclosures of which are incorporated by reference herein.
ICs having self-test or calibration features and using on-chip noises are described in the above-referenced Shrinkle, Ziperovich, and G. Evans et al. Shrinkle and Ziperovich describe ICs which are tested with digital noise generators. These digital noise generators create white Gaussian noise using digital logic circuits which are switched in a pseudo-random sequence. However, such digital noise generators are not useful for testing the noise figure and insertion gain of an RFIC because the noise generators do not create noise at high enough frequencies to match the input frequencies of RFICs. G. Evans et al. use a noisy complementary metal oxide semiconductor (CMOS) operational amplifier to generate white noise, but such a noise source is also not useful for testing the noise figure and insertion gain of an RFIC because the noise is not at high enough frequencies.
Roeder et al. describe a system which is self-tested with an RF noise source at high frequencies. However, the system and noise source are not contained on an RFIC. Seabaugh, U.S. Pat. No. 5,554,860, the disclosure of which is incorporated by reference herein, describes a noise generator using a resonant tunneling transistor. However, the noise source is not used for self-test of an RFIC or system, and the noise source is not contained on an RFIC.